共查询到20条相似文献,搜索用时 15 毫秒
1.
I. A. Fedorov 《Journal of Engineering Physics and Thermophysics》2011,84(1):171-178
Measurements have been made of gasdynamic characteristics of the flow of the active medium as well as energy and spectral
characteristics of radiation generated by a continuous chemical HF laser with a radially expanding nozzle unit. Based on the
analysis of measurement results, the flow structure of the active medium has been determined, which is formed by the “nozzle–injector”
reactant mixing scheme. It has been shown that only a part of the active medium is involved in the radiation generation. Measures
for improving the efficiency of its use have been proposed. 相似文献
2.
A. S. Boreisho V. F. Lebedev V. V. Lobachev A. V. Morozov 《Journal of Engineering Physics and Thermophysics》1984,47(1):781-786
A mathematical model of a gasdynamic laser with parallel supersonic mixing of the components and its applications to the choice of the geometrical characteristics of the nozzle unit of honeycomb construction are presented.Notation T
static temperature
- u
velocity
- P
pressure
-
molecular weight
- ei
average number of vibrational quanta
- k
amplification ratio for a weak signal
- I
radiation intensity
- i
molar fraction of the component in the mixture
- *
displacement thickness
- r, d
current radius and diameter of the nozzle
-
angle of inclination of the generating profile of the nozzle and characteristic temperature
- h
enthalpy
- G
flow rate
- L
characteristic length
- A/A*
expansion ratio of the nozzle
- Tw
wall temperature
- ¯Tw=¯Tw/To
temperature factor
- =E
a
/E*
nozzle efficiency
- E
stored vibrational energy
- X=X/(ra1 + ra2)
dimensionless coordinate
Indices 1
radiating gas stream
- 2
exciting gas stream
- 0
stagnation value
-
a, *,
values at the cut of the nozzle, in its critical cross section, and beyond the compression shock in the cross section of the nozzle cut
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 53–59, July, 1984. 相似文献
3.
É. N. Abdullin A. M. Efremov B. M. Koval’chuk V. M. Orlovskii A. N. Panchenko É. A. Sosnin V. F. Tarasenko A. V. Fedenev 《Technical Physics Letters》1997,23(3):193-195
The development of a high-power HF laser pumped by a chemical nonchain reaction initiated by a radially converging electron
beam is reported. A radiation energy of ∼ 115 J with an efficiency of ∼ 8% in terms of deposited energy has been achieved
in a mixture with an active volume of ∼ 30 liters. It is shown that because of the high SF6 density, the total pressure jump in SF6–H2(D2) mixtures caused by the electron beam injection and the chemical reactions is several times smaller than that in the active
mixtures of exciplex lasers for the same input energies. This factor considerably facilitates the development of wide-aperture
HF and DF lasers with an SF6 fluorine donor pumped by an electron-beam-initiated chemical nonchain reaction.
Pis’ma Zh. Tekh. Fiz. 23, 58–64 (March 12, 997) 相似文献
4.
O. A. Evtikhieva 《Measurement Techniques》2006,49(10):1027-1032
The problem of the refraction of a laser sheet in a transparent spherical nonuniformity, for example, in the liquid of a thermal
lens, is solved. Equations of the projection of the laser sheet, passing through the nonuniformity, are obtained. It is shown
that by using projections of the laser sheet one can determine the sign of the nonuniformity gradient and its order of magnitude,
and also establish the parameters of the specified model of the nonuniformity.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 49–52, October, 2006. 相似文献
5.
Translated from Izmeritel'naya Tekhnika, No. 12, pp. 11–12, December, 1989. 相似文献
6.
Active phase matching of multiline HF laser beams by means of a phase-locked Mach-Zehnder interferometer was demonstrated by locking the interferometer to the central interference fringe at zero optical path length difference. The central fringe could be found by varying the spectral content of the input beam. Laser amplification in one leg of the interferometer decreased fringe visibility without adversely affecting locking. Single-line fringe patterns produced by an array spectrometer (while the interferometer was operated in its scanning mode) were analyzed to show that no significant dispersion occurred in the amplifier. The techniques developed have potential for measuring dispersion mismatch between larger parallel amplifiers. These experiments demonstrated in principle that a number of multiline HF amplified beams can be recombined and phase-matched to produce a high beam quality output beam. 相似文献
7.
ObjectivesThis study investigated the photopolymerization-induced shrinkage properties of conventional methacrylate-based composites modified by a novel spiro-orthocarbonate (SOC) expanding monomer.MethodsThe epoxy monomer and SOC expanding monomer were added to a methacrylate-based resin matrix at five different ratios ranging from 20 wt.% (SOC + Epoxy) (group 1) to 60 wt.% (SOC + Epoxy) (group 5). Volumetric shrinkage and contraction stress developing after polymerization were measured using X-ray micro-computed tomography and a universal testing machine, respectively.ResultsThe volumetric shrinkage of the resin composite samples ranged from 0.92% (group 5) to 3.85% (control group) 30 min after light curing. Group 5 had the lowest volumetric shrinkage (p < 0.05), followed by groups 4, 3, 2 and 1. The contraction stress of the materials ranged from 1.86 MPa (group 5) to 3.56 MPa (control group). The lowest contraction stress was also observed in group 5, 30 min after curing (p < 0.05).ConclusionIncluding SOC expanding monomer reduced volumetric shrinkage and contraction stress of composites in comparison with conventional methacrylate-based composites. 相似文献
8.
《Advanced Powder Technology》2023,34(7):104058
The powder distribution and interaction between the laser beam and powder flow affect the deposition quality during the process of laser direct energy deposition with a continuous coaxial nozzle. In this paper, some key analytical formulae related to the laser beam-powder flow interaction are comprehensively deduced and validated. The powder distribution formulae for different regions are first established considering the divergence angles of powder jet. The energy attenuation formulae of laser beam passing through the powder flow are derived considering the change of powder distribution from annular to circular Gaussian modes. The temperature formulae of powder particles passing through the laser beam are derived based on a proposed temperature formula with the solid-liquid phase transition, and the powder temperature is also further analyzed. These formulae are validated by published deposition examples and used to analyze the laser beam-powder flow interaction. 相似文献
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10.
The present work studies a self‐similar high‐speed expanding crack of mode‐I in a ductile material with a modified cohesive zone model. Compared with existing Dugdale models for moving crack, the new features of the present model are that the normal stress parallel to crack faces is included in the yielding condition in the cohesive zone and traction force in the cohesive zone can be non‐uniform. For a ductile material defined by von Mises criterion without hardening, the present model confirms that the normal stress parallel to crack face increases with increasing crack speed and can be even larger than the normal traction in the cohesive zone, which justifies the necessity of including the normal stress parallel to the crack faces in the yielding condition at high crack speed. In addition, strain hardening effect is examined based on a non‐uniform traction distribution in the cohesive zone. 相似文献
11.
A. S. Boreisho V. V. Naumov V. A. Reisig A. G. Trofimovich V. V. Lobachev 《Journal of Engineering Physics and Thermophysics》1987,52(5):530-536
The characteristics of the flow and heat transfer in the nozzle grid of a gas-dynamic laser in the presence and absence of cooling of the blades are studied numerically in a conjugate formulation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 5, pp. 736–743, May, 1987. 相似文献
12.
We present experimental results on the intracavity generation of radially polarized light by incorporation of a polarization-selective mirror in a CO(2)-laser resonator. The selectivity is achieved with a simple binary dielectric diffraction grating etched in the backsurface of the mirror substrate. Very high polarization selectivity was achieved, and good agreement of simulation and experimental results is shown. The overall radial polarization purity of the generated laser beam was found to be higher than 90%. 相似文献
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Nanda Gopal Sahoo Mitali Kakran Lin Li Zaher Judeh Rainer H. Müller 《Materials science & engineering. C, Materials for biological applications》2011,31(2):391-399
A spray drier with a modified multi-fluid nozzle was used to prepare microparticles of a poorly water-soluble antimalarial drug, artemisinin (ART), with the aim of improving its dissolution in water. ART was co-spray dried with a hydrophilic polymer, polyethylene glycol (PEG). The differential scanning calorimetry and X-ray diffraction studies showed that the crystallinity of ART decreased after spray drying. Compared to the physical mixture of ART and PEG, the amorphous phase of ART in the spray dried ART–PEG composites increased, which depended on the weight ratio of drug to polymer. The phase-solubility studies revealed that the aqueous solubility of ART was improved by the presence of PEG. The dissolution of ART from the spray dried ART–PEG composites was more rapid than that from their respective physical mixture and the original ART powder. For example, the dissolution of ART from the spray dried ART–PEG composite (1:6) was 6.5 times higher than that from the original ART powder in the first 30 min. In the mathematical modeling, the Weibull and Korsemeyer–Peppas models were found to best fit to the in vitro dissolution data and then the drug release mechanism was considered as the Fickian diffusion. 相似文献
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19.
Zhang Y 《Applied optics》2010,49(32):6217-6223
The theoretical analyses in this paper show that a highly focused double-ring radially polarized Laguerre-Gaussian beam with a topological charge of 1 (R-LG(11)) can generate a small three-dimensional (3D) dark spot surrounded by an almost 100% uniform light shell in all directions. The cleanness and size of the 3D dark spot, the uniformity and strength of the light shell surrounding the dark spot, and the light efficiency all depend on the truncation parameter β of the R-LG(11) beam and the numerical aperture (NA) of the system. When β=1.6 and the NA is close to its utmost, an almost 100% uniform light shell surrounding the 3D dark spot can be achieved and the dark spot is very clean. If the NA is lowered but β is increased to 1.95, we can also achieve an almost 100% uniform light shell and light efficiency can reach 90%, but the disadvantage is that the center of the dark spot is not too clean. A not-too-clean 3D dark spot, if the light shell surrounding it is very uniform, is acceptable for many applications. Therefore, 3D dark spots surrounded by a high uniform light shell, generated by simply adjusting the truncation parameter of the R-LG(11) beam and the NA of the system, are useful for superresolution fluorescence microscopy, dark spot microscopy, and the dark spot trap. 相似文献
20.
Due to their attractive mechanical properties, bioinert zirconia bioceramics are frequently used in the high load-bearing sites such as orthopaedic and dental implants, but they are chemically inert and do not naturally form a direct bond with bone and thus do not provide osseointegration. A CO2 laser was used to modify the surface properties with the aim to achieve osseointegration between bioinert zirconia and bone. The surface characterisation revealed that the surface roughness decreased and solidified microstructure occurred after laser treatment. Higher wettability characteristics generated by the CO2 laser treatment was primarily due to the enhancement of the surface energy, particularly the polar component, determined by microstructural changes. An in vitro test using human fetal osteoblast cells (hFOB) revealed that osteoblast cells adhere better on the laser treated sample than the untreated sample. The change in the wettability characteristics could be the main mechanism governing the osteoblast cell adhesion on the YPSZ. 相似文献